1. Field of the Invention
The present invention generally relates to an improved structure of an organic electro-luminescence (to be abbreviated as xe2x80x9cELxe2x80x9d hereinafter) device, characterized in that a compartment is disposed in the periphery of a sealing case surrounding an organic layer and an opposed electrode. In the compartment, there is disposed a drying substance for moisture absorption, so as to prevent the generation of dark spots and prolong the lifetime of the device.
2. Description of the Prior Art
The organic EL device has attracted tremendous attention due to its advantages over other display panels. These advantages include a larger visual angle, shorter response time, a smaller dimension in thickness, lower power consumption, simpler fabrication, no need for backlighting, and the ability for light emitting in a full color range.
Please refer to FIG. 1, which is a cross-sectional view showing the structure of an organic EL device in accordance with the prior art. The organic EL device is characterized in that a transparent electrode 12 is formed on a substrate 11, and on the transparent electrode 12 there are an organic layer 13 which comprises a hole injection layer, a hole transport layer, an organic emitting layer or an electron transport layer, an opposed electrode 14 and an sealing case 15, where all the layers in the organic layer 13 are formed by evaporation in turn. Since in an organic EL device the light is generated when the electrons and holes from the transparent electrode 12 and opposed electrode 14 combine in the organic layer 13 to excite the organic emitting layer, it is inevitable that heat is generated during the luminescence process. Once the heat encounters the moisture existing inside the sealing case 15, dark spots due to oxidation will be formed on the surface of the organic layer 13. The existence of such dark spots adversely affects the luminescence qualities such as luminescence intensity and luminescence uniformity of an organic EL device. More seriously, the lifetime of an organic EL device may be substantially shortened.
In order to overcome the image defects due to the undesirable dark spots, some companies have developed a number of prior art organic EL displays to improve the image quality. For example, in the Japanese Patent Nos. JP-A-363890 and JP-A-5-114486, it is disclosed that liquid fluorinated carbon is disposed inside the sealing case 15 to effectively remove the heat generated during the luminescence process. In the Japanese Patent No. JP-A-5-41281, it is disclosed that dehydrating agents such as a synthetic zeolite are mixed in the liquid fluorinated carbon to effectively remove the moisture existing in the periphery of the device. Moreover, in the U.S. Pat. No. 5,962,962, entitled xe2x80x9cMethod of encapsulating organic electroluminescence device and organic electroluminescence devicexe2x80x9d, it is disclosed that a silicone oil or a silicone grease is used as a protective liquid to remove the existing moisture.
The above prior arts can reduce the generation of dark spots to some extent; however, the dehydrating agents such as liquid fluorinated carbon may add difficulty to the fabrication process, which is unfavorable for fabrication integration and reduction in cost.
Accordingly, a second prior art structure of an organic EL device is proposed as shown in FIG. 2. In the U.S. Pat. No. 5,882,761, entitled xe2x80x9cOrganic EL elementxe2x80x9d, it is disclosed that a drying substance 17 is attached to the inner surface of a sealing case 15 showing a sealing agent 18 and an internal space 19 is formed between the drying substance 17 and an opposed electrode 14. The solid-state drying substance 17 absorbs the moisture existing inside the sealing case 15, so as to prevent the generation of dark spots.
Even though the U.S. Pat. No. 5,882,761 can overcome some of the problems in the prior arts, it still has the following drawbacks:
1. The drying substance is attached in the direction right above the organic layer and the opposed electrode. Therefore, when the device is hit against an external force, the drying sbustance may fall off and directly hit the organic layer or the opposed electrode. In this case, the device will damage.
2. The drying substance is attached in the direction right above the organic layer and the opposed electrode. In addition, there must be a vertical gap between the drying substance and the opposed electrode. Therefore, the total height is increased, which becomes a limit when it comes to designing a downsized device.
Therefore, the present invention has been made to solve such problems in view of the forgoing status and to further provide an improved structure of an organic electro-luminescence (EL) device, incorporating a sealing case that can effectively prevent the damage when being hit by an external force and prevent the generation of dark spots, so as to prolong the lifetime of the device.
It is the primary object of the present invention to provide an improved structure of an organic EL device, in which there is disposed a drying substance in a compartment in the periphery of the sealing case to absorb the moisture around the organic layer, so as to prevent the generation of dark spots and prolong the lifetime of the device.
It is another object of the present invention to provide an improved structure of an organic EL device, in which a drying substance is stored in a compartment that is distant from the perpendicular direction to the organic layer, so that the drying substance does not hit the organic layer when it falls off due to an external force. In this case, the probability that the organic layer is damaged is lowered.
It is still another object of the present invention to provide an improved structure of an organic EL device, in which a drying substnace is disposed in a non-perpendicular direction to the organic layer, so that there is not necessarily a vertical gap between the drying substance and the opposed electrode. Therefore, the total height is decreased, which is favorable when it comes to designing a downsized device.
It is still another object of the present invention to provide an improved structure of an organic EL device, in which a drying substance is disposed in a non-perpendicular direction to the organic layer, so that whether the drying substance may fall off and directly hit the organic layer or the opposed electrode does not become the key issue concerning the lifetime of the device. In this case, the fabrication process can be simplified.
In order to achieve the foregoing objects, the present invention provides an organic EL device, comprising: a substrate; at least one transparent electrode on the surface of said substrate; an organic layer, comprising at least one organic emitting layer, formed on the surface of said transparent electrode; an opposed electrode, formed on said organic layer; a sealing case, attached to the surface of said substrate by a inner sealing pad, thereby forming an inner gap to surround and isolate said organic layer and said opposed electrode; and a sealing ring, disposed in the periphery of said sealing case, attached to the surface of said substrate by a bottom sealing pad and attached to the sidewall of said sealing ring with a lateral ring body of said sealing ring by a side sealing pad; wherein there is a drying substance disposed in a compartment enclosed by said sealing ring.
Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings are incorporated in and constitute a part of this application and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.